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Biology - Microbiology > Biochemistry - Bacterial Conjugation > Flashcards

Biochemistry - Bacterial Conjugation Flashcards

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1
Q

Conjugation

A

Unidirectional transfer mechanism in GPB and GNB.

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2
Q

In what communities does conjugation occur?

A

Soil communities, plant surfaces, sewage systems etc.

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3
Q

What is the function of conjugation?

A

Mediate gene transfer of those genes that allow increased fitness, like metabolic capabiltiies, resistance and virluence,

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4
Q

Why are plasmids important for conjugation?

A

They contain the genome necessary for self maintenace for transfer from mother to daughter cell.

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5
Q

What is the BRIEF of conjugation within the donor cell?

A

Expression of plasmid tra genes
Relaxosome plasmid processing
Conjugative pilus mating pair formation
Transfer by T4SS

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6
Q

What is the brief of conjugation within the host cell?

A

Plasmid establishment like host defense proteins.
Leading gene expression
Covnersion of ssDNA plasmid to dsDNA

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7
Q

Tra Gene

A

Genes necessary for transfer of genetic material in both GPB and GNB

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8
Q

What does the Tra Gene contain?

A

The expressive components for mating pair formation between pilus and T4SS and relaxosome proteins.

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9
Q

What is tra gene expression mediated by?

A

TF, envrionmental conditons, cell cycle progression.

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10
Q

Where do tra gene TF do once stimualted?

A

Gather in the operon controled by the Pgamma promoter

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11
Q

Operon

A

A cluster of genes transcribed together to give a single mRNA

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12
Q

Why are tra genese physiologicallly repressed?

A

It is un-benefical to express them during non-conjugative states.

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13
Q

What is requried for tra gene activaiton?

A

A cascade by TraJ production activating Py promoter transcribing proteins mediating other cascades expressing the T4SS and Pilus proteins

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14
Q

What is repression and regulation mediated by?

A

FinOP system and H-NS copy

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15
Q

How does FinOP system regulate tra gene repression?

A

FinP is complementary to stem loop of TraJ mRNA, binding preventing ribosome binding, preventing translation.

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16
Q

How does H-NS regulate tra gene expression?

A

Regulates mainly promoters involved in the cascade

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17
Q

Why and how does H-NS allow plasmids to be phase dependent?

A

Its concentration varies during growth, like exponetnial, lag phase etc.

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18
Q

What follows tra gene expression?

A

F pilus synthesis

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19
Q

F Pilus

A

A pili mediating wall-to-wall contact between mating partners

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20
Q

What proceeds F pilus specificity binding?

A

Plasmid processing by the relaxosome

21
Q

How does relaxosome process the plasmid?

A

Excision of the DNA, extrusion of formed ssDNA

22
Q

How does relaxosome structure relate to its function?

A

Contains proteins with transesterase activity and ability to unwind plasmid DNA

23
Q

What is the process of RCR in plasmids?

A

Excision for two free ends, the 5’ phoshapte and 3’ OH, used for priming by DNAP 3, elongating leading strand, unwinding parental double helix, releasing newly synth DNA through excision.

24
Q

Where does RCR and T-Strand replication occur?

A

RCR in the donor whilst T-Strand in the recipient cell.

25
Q

What follows RCR?

A

Transfer by T4SS

26
Q

What role do T4CP play is transfer of the plasmid DNA?

A

They mediate interactions between relaxosome and T4SS

27
Q

What happens first in recieving cell in conjugation?

A

T-strand refolding by helicase activity within the relaxase enzyme internalised.

28
Q

What does the relaxase do in tandem with T4CP?

A

Translocate T strand through the pore.

29
Q

When does ligase activity occur on T-Strand?

A

When both extremities of the OriT are brough togeterh by the relaxase.

30
Q

What systems do recipient cells employ to deter plasmid acquisiton?

A

Restriction Endonucleases and CRISPR-cas9 systems

31
Q

Restriction Modification System

A

A bacteria primitive immune system where restriction enzymes nick unmethylated DNA sequences.

32
Q

How does the RMS prevent self DNA degradation?

A

Methyltransferases binding its own genome to prevent binding.

33
Q

How do plasmids avoid the RMS?

A

Producing proteins that mimic resitriction endonuclease binding sites, competetively inhibiting them.

34
Q

What bacteria contain anti-plasmid crispr capabilities?

A

Listeria, Streptococcus and staphylococcus.

35
Q

What happens after T Strand refolding?

A

Conversion to dsDNA.

36
Q

Why is leading strand directed translocation important?

A

Within the leading strand, essential proteins important in DNA protection and replication efficiency are found.

37
Q

SOS response

A

This detects abnormal ssDNA levels. which are usually associated with DNA damage.

38
Q

What does the SOS response do when ssDNA is detected?

A

RecA is recruited to ssDNA forming presynaptic filaments with stimulatse autocatalytic cleavage of LexA proteins TRIGGERING sos causing inhbiiton of cell division with recruitment of nucleases and DNA factors to degrade ssDNA

39
Q

How can plasmids aboid SOS response?

A

Inhbition of RecA and chromosomal ss binding proteins binding ssDNA to increase resistance.

40
Q

Function of SSB proteins?

A

Protect the ssDNA from enzymatic degradation and increasing processivity of DNAP.

41
Q

What occurs after dsDNA formation?

A

Replicaiton and segregation into daughter cells.

42
Q

Why are some plasmids restricted to hosts similar to the donor?

A

RepF1A replicon RepE inability to form stable interactions with host helicases

43
Q

Transconjugant

A

A bacteria recieving plasmid contect from another.

44
Q

What is the final step of plasmid conjugation?

A

Phenotypic conversion to the transconjugant.

45
Q

What are common genes improving bacterial fitness found in Plasmids?

A

Virulence, biofilm formation, ab resistance etc.

46
Q

How is plasmid acquistion deemed energetically favourable?

A

The increased burden of more genetic material is outweighed beneft new genome content provides

47
Q

What is the functional importance of conjugation?

A

Improves bacterial population survivalbility and function.

48
Q

Replicon

A

Virus like particles entering target cells and undergoing limited protein synthesis

Biology - Microbiology (19 decks)

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